51 inches in diameter! Imagine wielding a 1/2 sheet of plywood to protect yourself.
Imagine *not* having such a shield. :^)
Being round it would be a little less than a half sheet. I’m guessing about 25-30 lbs. The weight of such shields usually was borne not just by the hand but also the forearm. Of course the warriors trained a lot and would be used to it over time. On the other hand, literally, the Roman gladius only weighed a couple of pounds so maybe they looks like Popeye!